Arrangement for controlling tube senders



.May 3, 1927.

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4 away is made ofradioapparatus, andhas for its Patented May 3, 1927;

PATIENT f w -y ALFRED SEMM AND WALTER "SCI-IAFFER, for BERLIN, GERMANY, AssIGNoRs'ro on SELLSCHAFT rim nRAHrtosE TELEGRAPHIEM. B. rr for BERLIN, GERMANY, A

r on or DELAWARE.

coRr-oRA'rIoNlor GER Y, Annnnnro oonronArroir or AMERICA, A conpom.

I ARRANGE nN'r FOIRACONTBOLLING TUBE smrnrms.

Application filed February 16,"1925,"Seria1 No. 9,549, andin Germany December 5, .1923. i

V Our invention relates to means for controlling tubePsenders; Lin signalling wherein, use

object to providesuch an arrangement which will, effectively control, the send ng tubes .to

give the desired signal and yet will not cause said tubes to be destroyed throughundue heating when, signals are not a being sent. This'inv'ention is principally useful when the plate current is derived from an. alternating current source and then suitably rectified since; the voltage regulation ofisuch a plate-supply arrangement isfinherently' Poor." 1; T

' Other' objectswill' be. apparent from the following description and claims when consi'dered with the accompanying drawing, in

1i i'gure 1;shows a formlof ourjinvention using a selfsexcited controlling. tubeand a separately excited controlling tube for transmission. Fig. 2 shows an arrangementsim 1 ilar to F1, and Fig. 3 is a modification of the drawing aslshown in Fig. 1 applying the idea of the invention totelephonework. In arrangements in-which a tubetrans-v mitter is fed byia secondselzt-excited tube transmitter, the operation of keying injthe case of telegraphy work, and the. modulation intelephonyl'c'an be accomplished in. various ways. The self-excited tube transmitter (is an oscillation generator, while the controlled tube transmitter isan amplifier. lnfthefmajorityotca'ses action is-brought upon the grid of these'lf-exc'ited or ofthe amplifier tube. for the reason that the requisite keying or modulating energy is small. a a In what way the grid keying or, the modulationshould best be a'ccomplished is well known, and; similarly well known is .the keying or. themodulation of the grid ofaseparately controlled tube. i

Inboth kinds of. action, however, certain Y inconveniences r manifest themselves which.

are observed in and-are peculiar to this combination 'of-a'separate amplifier-ltubeand a self-excited. tube. These difliculties shall first be discussed in the following beforethe idea underlying the invention is further dis,- cusse'd. 1, According to the old methods, the arrangement was provided witha self-excited transmitting tube, in which the'selfeexcited tube getsits self-excitation by means of a three po nt connectionon an oscillation circuit. Coupled with this oscillation circuit. is a secondfoscillationcircuit to the condenser of which the grid member ofthesecon'd-tube is connected. This second tube is arranged to feed its energy upon an antenna in. any well known manner. 1 c

For the purpose of keying or modulating it has been customary to connect thegrid of the self-excited tube toitsfoscillation circuit stop entirely (asduring keying and speech interinissions) it is well cknownlthatthere flowsin the tube an idle current which tends, to heat the anode. The tube being unloaded at this time, the anode voltage is higher than during load. This is a phenomenon that can,

not be avoidedwhen the plate current is derlved from rectified alternating current. 1

Thisdisadvantage maybe rendered harmless f the grid of thesep'arately excited tube is acted uponor influenced bya keying or modulater deviceoperating directly on thesaid tube k insteadof on the self-excited tube. Insuch a case thegrid of the self-excitedtube would.

be connected directly with ,the'tube oscilla:

tion circuit and thegridof the separately excited tube would be connectedv with; its 0:- cillatory circuit byway of condenser and with the'filament by way of; the choke coil and .a keying or modulation device. If,by the latter method, the direct grit potential-ofseparately excited tube is {compensated, neutralized or greatly diminished,

- theitubej oscillation circuit willbe subject to less damp ng-yln otherwords,fmore energy will be taken away from the oscillatory circuit of "the first transmitting tube. If the first transmitting tube and its oscillatory circuit were previously properly coupled, theanode alternating current will then be caused to dropin the same, with the consequence that the heatingiof the anode is raised in that tube. It, in this scheme, both tubes are fed from the sameanode voltage source,;i. e. by rectified alternating current, thevoltage of which will. greatly increase when the load is taken off the second transmitting .or sep arately excited tube, it will be seen that the heating of the first transmitting or self-excited tube is apt to assume inadmissibly high values.

Hence, it seems necessary that the grid current of both tubes be simultaneously inte rupted or diminished during the intermissions in key or speech work. This could be done, e. g, by having distinct keyingand modulator devices for the two tubes. Yet, apart from the greater outlay in equipment, such an arrangement would be unsuitable, because two keying and modulating devices could be operated in exact'synchronism only with great difliculty.

Now, the present invention obviates all of the said difficulties by means of a method according to which the grid discharge circuit of the self-excited tube and the separately excited tube transmitters are simultaneously keyed or influenced by a modulator device. An arrangement of the kind embodying means to practice this method consists in having the grid discharge circuit of the selfexcited transmitter and the separately excited transmitter provided with a common branch containing the keying or the modulating device, and which, as a consequence, influences both grids simultaneously.

The arrangement according to this plan has been so chosen that the grids are blocked against one another and the common branch with reference to the grids by the aid of high frequency blocking means. Fig. 1 illustrates by way of example in what way the idea could be carried into practice. The grids of tube a and b are blockedagainst the circuits 0 and (Z by the aid of condensers f and f in a capacitive manner, while being interconnected by way of high'frequency choke coils g and g. The common point is of the choke coils is connected with the cathode pole Z common to both filaments by way of the keying or modulating device h. In order to safeguard point 76 against all high frequency potentials, a path 8 for the current is created parallel with reference to it which is impassable for the direct current, said path offering as low a resistance as feasible to the flow of high frequency current.

Fig. 2 shows the application of the idea underlying the invention to telegraphy work. The keying organ is the telegraphy key it, a condenser 3 being connected'conveniently in parallel thereto.

Fig. 3 shows the application of the idea to telephony Work. The modulator-means consists of the tube 6 whose filament, in well known manner, is connected with the grids of the transmitter tubes a and Z) whereas its anode is put in conducting connection with the filaments of both tubes. Parallel relative to the anode and cathode of the modulator tube 2?, there is again arranged in convenient manner the condenser 8, while the speech modulation is produced by way of speech modulating transformer 71.

Having described several embodiments of our invention, we are entitled to all modifications thereof as fall fairly within the scope of the following claims:

1. An arrangement for wireless telegraphy and telephony comprising a self-excited con 2. An arrangement for wireless telephony and telegraphy comprising a self-excited controlling tube and a separately excited controlled tube for transmitting, means by which the grid circuits of each of the said tubes are simultaneously subjected to modulation whereby heating of the anode members of each tube may be minimizedat the no load period, a branch circuit common to each of the said grid circuits, said means for producing modulation being contained in the said branch circuit, means to block the grids members of said tubes against one another with respect to high frequency currents, said blocking means comprising high frequency choke coils inserted in the connection between the two grid members, and a high frequency path arranged in parallel to said modulating device.

- 3. In an arrangement for wireless telegraphy and telephony'an oscillator and an amplifier tube, a connection between the grid elements of eaclrof said tubes, said connection being made by way of a high frequency choke coil,"a connection between the cathode members of said tubes, a branch circuit common to each tube between the said grid and cathode connections, a modulating device arranged in said common branch circuit and a condenser arranged in parallel to said modulating device.

4. In an'arrangement for wireless telephony, a controlling and a controlled tube for transmitting, high frequency choke coils through which the grid members of said transmitters are connected, a connection between the cathode and members of said tubes, and a third connection by way of a modulating device having one terminal connected between the said choke coils and the second terminal connected to the cathode connection, said modulating device comprising a third tube to which a modulation means is joined.

jecting the grid of each tube to modulation for transmitting, a connection between-the grid elements of said tubes, said connection.

being formed through high frequency choke coils whereby the said grids are blocked with respect to high frequencies relative to each other, a connection between the cathode members of the said tubes, a branch circuit common to each of said tubes arranged bemodulating device for simultaneously sublocated in said branch circuit, said ,modulating device comprising a third tube having its anode member connected to the cathode r point of-the branch circuit, a modulating circuit havingone end connected to the grid member of said modulating tube and its opposite-end connected to the grids of the said transmitting tubes, and a condenser between the) cathode and anodeof said modulating tu e.

ALFRED SEMM.

A TER SCHAJFFERQ 

